JP5592909B2 - Magnetic memory - Google Patents

Description

  Embodiments described herein relate generally to a magnetic memory.

  One of the memories is a domain wall memory. The domain wall memory uses a magnetic material in a portion for recording information. Information is expressed by the structure of the magnetic domain formed by the magnetization of the magnetic substance, the position of the domain wall, or the spatial distribution of the magnetization in the domain wall, and held. A magnetic memory called a racetrack memory is also one of domain wall memories.

  If the magnetic domains are arranged in a line in the magnetic material, the domain wall memory can be densified, so the shape of the magnetic material that holds information is linear or curved. When a current is passed in the direction in which the magnetic domains are arranged, the domain wall moves in parallel along the direction in which the current flows. In the domain wall memory, this phenomenon is used to move the domain wall after reversing the magnetization of a part of the stretched magnetic material, or to move the domain wall after converting the magnetization state of a part of the magnetic material into an electric signal. Thus, an information write / read operation is performed.

US Pat. No. 6,834,005

  A large capacity of the domain wall memory can be realized by extending a large number of magnetic bodies for recording information in the direction perpendicular to the wafer surface and mounting them at high density as thin wires. On the other hand, in order to form a fine line, the wafer is finely processed in advance to form a three-dimensional structure such as a hole or a columnar structure, and a magnetic thin film is formed on the surface of the three-dimensional structure and subdivided to form a fine line. Alternatively, a method is adopted in which a hole is dug in advance using an electrochemical reaction and filled with a magnetic material to form a fine wire. In either case, it is necessary to form an electrode used for fine processing for thinning and electrochemical reaction, which causes an increase in manufacturing cost.

  Therefore, the present embodiment provides a magnetic memory that can reduce the manufacturing cost.

  The magnetic memory according to the present embodiment has a magnetic body structure extending in the first direction and having an annular cross section in a plane perpendicular to the first direction, and an outer surface along the first direction of the magnetic body structure. And a reference portion including a magnetic material provided on a part of the surface of the nonmagnetic layer opposite to the magnetic material structure.

FIGS. 1A and 1B are diagrams showing a magnetic memory according to the first embodiment. FIGS. 2A and 2B are diagrams illustrating an example of information stored in a magnetic memory. FIG. 3A to FIG. 3D are diagrams for explaining the state of information written to and read from the magnetic tube. FIGS. 4A to 4E are diagrams for explaining the shift operation. FIG. 5A to FIG. 5E are diagrams for explaining a write operation. The figure which shows the peripheral circuit group connected to a magnetic memory. FIGS. 7A to 7D are timing charts showing an example of the initialization operation. 8A to 8D are diagrams for explaining a write operation. FIG. 9A to FIG. 9D are timing charts showing an example of the write operation. FIG. 10A to FIG. 10D are diagrams illustrating a read operation. FIG. 11 is a timing chart showing the read operation shown in FIGS. 12A to 12E are timing charts showing an example of a read operation. FIG. 3 is a front view showing a manufacturing process of the magnetic memory according to the first embodiment. FIGS. 14A and 14B are views showing a manufacturing process of the magnetic memory according to the first embodiment. FIGS. 15A and 15B are views showing manufacturing steps of the magnetic memory according to the first embodiment. FIGS. 16A and 16B are diagrams showing manufacturing steps of the magnetic memory according to the first embodiment. FIGS. 17A and 17B are views showing a manufacturing process of the magnetic memory according to the first embodiment. FIG. 18A to FIG. 18C are diagrams showing examples of the longitudinal sectional shape of the magnetic tube. FIGS. 19A and 19B are schematic views showing the magnetic memory according to the first embodiment. 20A and 20B are schematic views showing a magnetic memory according to the second embodiment. The top view of the magnetic memory by 3rd Embodiment. The front view of the magnetic memory by 3rd Embodiment. The bottom view of the magnetic memory by 3rd Embodiment. FIG. 6 is a top view for explaining an example of a write operation of a magnetic memory according to a third embodiment. The front view explaining an example of write-in operation of the magnetic memory of a 3rd embodiment. The front view explaining an example of write-in operation of the magnetic memory of a 3rd embodiment. The front view explaining an example of write-in operation of the magnetic memory of a 3rd embodiment. The front view explaining an example of write-in operation of the magnetic memory of a 3rd embodiment. The front view explaining an example of write-in operation of the magnetic memory of a 3rd embodiment. The figure which shows the peripheral circuit connected to the magnetic memory of 3rd Embodiment. FIG. 31A to FIG. 31I are timing charts showing an example of batch write operation of the magnetic memory according to the third embodiment. The top view of the magnetic memory by the modification of 3rd Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
1A and 1B show a magnetic memory element (also referred to as a magnetic memory cell) according to the first embodiment. FIG. 1A is a front view of the magnetic memory element 1 of the first embodiment, and FIG. 1B is a cross-sectional view taken along the cutting line AA shown in FIG. The magnetic memory element 1 according to the first embodiment includes a magnetic tube 10, an intermediate layer 16, and a reference unit 18. The magnetic tube 10 extends in the first direction (z-axis direction), and a cross section (cross section in the xy plane) orthogonal to the first direction has an annular shape. An intermediate layer 16 is formed on the outer surface of the magnetic tube 10. A reference portion 18 is provided in a region of a part of the outer surface of the magnetic tube 10 via an intermediate layer 16. In FIGS. 1A and 1B, the intermediate layer 16 is provided on the entire outer surface other than the end face of the magnetic tube 10, but is provided in a region where the reference portion 18 is provided. Also good. The inside of the magnetic tube 10 may be hollow. Alternatively, it may be embedded with a substance such as an insulator, a semiconductor, a ferroelectric, or a metal. The prospective angle α of the contact surface of the reference portion 18 and the intermediate layer 16 with the magnetic tube 10 viewed from the center of the magnetic tube 10 does not exceed 180 °.

  The reference unit 18 is a ferromagnetic material. As the ferromagnetic material, at least one element selected from iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), and chromium (Cr), platinum (Pt), palladium (Pd), An alloy with at least one element selected from iridium (Ir), ruthenium (Ru), and rhodium (Rh) can be used. For example, CoPt, NiFe, CoCrPt, or the like can be used as the ferromagnetic material. The properties of the ferromagnetic material can be changed by changing the composition, heat treatment or the like.

  The magnetization of the reference portion 18 is fixed in the direction of the arrow 19 (y-axis direction) shown in FIG. Further, as will be described later, in the magnetic tube 10, magnetic domains each divided by a domain wall serve as a memory, and information is written into the memory cell by the reference unit 18 using the spin torque transfer method, or information is read from the memory cell. Is read out. For this reason, the thickness t of the reference portion 18 in the direction in which the magnetic tube 10 extends (z-axis direction) is preferably smaller than the recording length described later, and is about 10 nm or more in consideration of the realizable domain wall width. In consideration of high-density recording, it is desirable that the thickness is 50 nm or less. There is a possibility that the magnetization direction of the reference portion 18 changes due to the reaction of the spin torque generated in the magnetic tube 10 when a current is passed. For this reason, it is desirable that the damping coefficient of the reference portion 18 is larger than the damping coefficient of the magnetic tube 10. In this case, the time required for the magnetization reversal of the reference unit 18 by the spin torque becomes longer. Therefore, when the current flow time is short, the magnetization of the reference portion 18 is difficult to reverse.

  In the present embodiment, the intermediate layer 16 is made of a tunnel insulating film material. Examples of the tunnel insulating film material include aluminum (Al), titanium (Ti), zinc (Zn), zirconium (Zr), tantalum (Ta), cobalt (Co), nickel (Ni), silicon (Si), magnesium ( Mg), an oxide containing at least one element selected from iron, nitride, fluoride, or oxynitride can be used. In addition, a semiconductor material having a large energy gap such as AlAs, GaN, AlN, ZnSe, ZnO, and MgO can be used.

  For the intermediate layer 16, for example, Ta, Ru, Pt, Pd, Ir, Cu, Au, Ag, Cr, and Al can be used as the constituent material. An alloy containing at least two of these elements may be used. Further, an alloy in which at least one of these elements is selected and combined with other elements may be used. A stacked structure of these elements may be used.

  The magnetic tube 10 is composed of a ferromagnetic material, a ferrimagnetic material, or an artificial lattice. As the ferromagnetic material, an alloy of at least one element selected from Fe, Co, Ni, Mn, and Cr and at least one element selected from Pt, Pd, Ir, Ru, and Rh is used. it can. For example, CoPt, NiFe, CoCrPt, or the like can be used as the ferromagnetic material. The properties of the ferromagnetic material can be changed by changing the composition, heat treatment or the like.

  As the ferrimagnetic material, an amorphous alloy of a rare earth such as TbFeCo and GdFeCo and a transition metal can be used. When these materials are deposited by selecting the production conditions, the magnetization tends to be easily oriented in the deposition direction, and can be used when the magnetization is desired to be provided in the direction perpendicular to the thin film surface. In addition, by adjusting the composition of rare earth elements Tb and Gd and transition metal elements Fe and Co, the exchange stiffness and the magnitude of magnetization can be changed, which is advantageous when modulating the behavior of the domain walls and magnetic domains in the magnetic tube. is there.

  As the artificial lattice, a laminated structure of a ferromagnetic material and an alloy of at least one element selected from Pt, Pd, Ir, Ru, Cu, Ag, Au, and Cr can be used. When the fabrication conditions and the film thickness of each layer are selected, the magnetization of the ferromagnetic tube 10 has an antiferromagnetic arrangement, so that the magnetization of the magnetic tube 10 can be adjusted. As the ferromagnetic material, an alloy of at least one element selected from Fe, Co, Ni, Mn, and Cr and at least one element selected from Pt, Pd, Ir, Ru, and Rh is used. it can. For example, CoPt, NiFe, CoCrPt, or the like can be used as the ferromagnetic material.

  Next, the principle of operation of the magnetic memory element 1 of this embodiment will be described with reference to FIGS. 2 (a) to 7 (b).

  As shown in FIG. 2A, the magnetic tube 10 can be magnetized so that the magnetic flux is closed in the magnetic tube 10. In FIG. 2A, the direction of magnetization of the magnetic tube 10 when viewed from the lower side upward along the extending direction of the magnetic tube (the z axis shown in FIG. 1A) is indicated by an arrow. There are two types of magnetization directions, clockwise and counterclockwise. The magnetic memory element 1 records information using these two states. In this specification, it is assumed that clockwise magnetization represents “0” and counterclockwise magnetization represents information “1”. The clockwise magnetization may represent “1” and the counterclockwise magnetization may represent information “0”.

  As shown in FIG. 2B, the magnetic tube 10 can take a multi-domain state in which the magnetic tube 10 is magnetized in a clockwise or counterclockwise direction by a portion of the magnetic tube 10. As shown in FIG. 2B, if the recording length is defined in the extending direction of the magnetic tube 10 (z-axis direction), this multi-domain state can be read as a bit arrangement. For example, the multi-domain state shown in FIG. 2B represents a bit arrangement 0100101101 counted from above the z-axis. In FIG. 2B, the white portion represents information “0” and the shaded portion represents information “1”.

  As described above, the magnetic memory element 1 includes the magnetic tube 10, the intermediate layer 16, and the reference unit 18. By using this, the multi-domain state is created and this magnetic domain state (stored in the magnetic domain is stored). Magnetization direction) can be converted into an electrical signal. With reference to FIG. 3 (a) thru | or FIG.3 (d), the operation method of the magnetization of the magnetic tube 10 and the conversion method to the electrical signal of a magnetic domain state are demonstrated.

  FIG. 3A and FIG. 3B show a method of manipulating the magnetization of the magnetic tube 10 with an electric current. As is well known, a current flows between the first and second ferromagnetic layers in a structure in which a nonmagnetic metal layer or insulating layer is sandwiched between first and second ferromagnetic layers called a spin valve. Thus, a spin torque due to the spin-polarized current is generated, and the magnetization directions of the first and second ferromagnetic layers can be controlled to be parallel or antiparallel. If the magnetization of one of the first and second ferromagnetic layers (for example, the first ferromagnetic layer) is fixed in a specific direction by structural contrivance, the other ferromagnetic layer (second ferromagnetic layer) Only the magnetization of the layer) is reversed by passing a current. When a current is passed from the first ferromagnetic layer (fixed layer) whose magnetization is fixed to the second ferromagnetic layer, the magnetization of the second ferromagnetic layer is reversed in a direction antiparallel to the magnetization of the first ferromagnetic layer, When current flows in the opposite direction, it reverses in the parallel direction. Also in the magnetic memory element 1 of the present embodiment, the magnetization of the magnetic tube 10 is controlled using the same physical phenomenon.

  Since the reference portion 18 has an easy magnetization axis in the extending direction (the y-axis direction shown in FIG. 1A), the reference portion 18 is directed in advance in one direction (FIGS. 3A to 3D). Magnetize in the right direction). By selectively using a material having a large shape anisotropy and a damping coefficient, the reference portion can perform the same function as the fixed layer in the spin valve. That is, the reference unit 18 functions as an electrode that allows a spin-polarized current to flow through the magnetic tube 10. In this specification, the direction in which the write current Iw flows from the magnetic tube 10 to the reference unit 18 through the intermediate layer 16 is positive. When a negative write current (−Iw) flows between the magnetic tube 10 and the reference unit 18 with respect to the magnetization of a part of the magnetic tube 10 due to the presence of the reference unit 18, the magnetization of the reference unit 18 is antiparallel. (FIG. 3 (a)), spin torque works. Conversely, when the write current is positive (Iw), the spin torque acts so as to be parallel (FIG. 3B). In the magnetic memory 1 of the present embodiment, when this is utilized and the magnetization of the portion of the magnetic tube 10 adjacent to the reference portion 18 is changed from “1” to “0”, as shown in FIG. By writing a negative write current (−Iw), the magnetization of the portion of the magnetic tube 10 is changed from parallel (direction indicated by a wavy line) to antiparallel (direction indicated by a solid line), thereby writing information. Further, as shown in FIG. 3B, in the case of “0” → “1”, a positive write current (Iw) is passed, and the magnetization of the portion of the magnetic tube 10 is antiparallel (the direction indicated by the wavy line). The information is written by making it parallel to the direction indicated by the solid line.

  Reading of information is performed by converting the magnetization direction of a part of the magnetic tube 10 adjacent to the reference unit 18 into an electric signal by using the tunnel magnetoresistance effect (TMR effect). Similar to the spin valve, in the magnetic memory 1 of the present embodiment, the magnetic tube 10 and the reference portion 18 are separated by the intermediate layer 16 made of an insulator, and the flowing current is a tunnel current. Therefore, when the magnetization of the magnetic tube 10 and the magnetization of the reference portion 18 are antiparallel, the resistance between the magnetic tube 10 and the reference portion 18 is higher than when the magnetization is parallel. In the configuration shown in FIGS. 3C and 3D, when a part of the magnetic tube 10 adjacent to the reference portion 18 has magnetization in the direction represented by “0”, the magnetic tube 10 The resistance to the reference unit 18 is in a high resistance state, and when it has a magnetization of “1”, it is in a low resistance state. A current is passed between the magnetic tube 10 and the reference unit 18, and a voltage dropping between the magnetic tube 10 and the reference unit 18 is used as a read signal.

  In the magnetic memory 1 of this embodiment, it is necessary to shift and move the magnetic domain with the domain wall generated by the write operation in the magnetic tube 10. In the magnetic memory 1, as shown in FIGS. 4A to 4E, a current is passed through the magnetic tube 10 to shift the domain wall. FIG. 4A shows the magnetic tube 10 in which the white portion is in the state “0” and the shaded portion is in the state “1”. There is a domain wall between the white part and the shaded part. In this domain wall, the magnetization direction is twisted.

  As shown in FIG. 4B, when a current is passed from the upper side to the lower side of the drawing, the domain wall shifts from the lower side to the upper side. The electrons flowing from the bottom to the top cause spin torque at the domain wall portion where the magnetization is twisted. This spin torque works to direct the upper magnetization in the direction of magnetization of the lower magnetic domain across the domain wall. As a result, the domain wall is shifted by the current while maintaining the size of the magnetic domain, that is, the length (recording length) of the magnetic domain in the extending direction of the magnetic tube 10. As shown in FIG. 4C, the domain wall shift continues while the current continues to flow, and when the direction of the flowing current is reversed as shown in FIGS. 4D and 4E, the domain wall shift direction is also reversed. To do. By combining the above write operation, read operation, and shift operation, information can be stored in the magnetic memory 1 and information can be read from the magnetic memory 1.

(Initialization operation)
Since the magnetization arrangement of the magnetic tube 10 immediately after the magnetic memory 1 is manufactured may change due to various factors, it cannot be predicted. Therefore, it is necessary to initialize the magnetization of the magnetic tube 10 before starting use.

  As in the prior art, in the case of a domain wall memory using magnetic thin wires, in principle, initialization is performed by directing the magnetization of the thin wires in one direction by applying an external magnetic field.

  On the other hand, since the magnetic tube 10 in the present embodiment is closed in the tube 10, the magnetized state cannot be made uniform even when an external magnetic field is applied. Therefore, the magnetic tube 10 is initialized by combining the write operation and the shift operation as shown in FIGS. The state before the initialization of the magnetic tube 10 takes a magnetization arrangement that is difficult to predict, as shown in FIG. Here, current flows from the reference portion 18 to the magnetic tube 10 to change the magnetization of a portion of the magnetic tube 10 adjacent to the reference portion 18 to the state “1” (FIG. 5B). If this state is the state “1” before the current flows, no change occurs. Subsequently, a negative shift current (-Is) is passed through the magnetic tube 10 to shift the domain wall downward by 1 recording length (FIG. 5C). In the present specification, the shift current Is is positive in the direction flowing from the upper side to the lower side as shown in FIG. 5E and negative in the direction flowing from the lower side to the upper side as shown in FIG. 5C. And These two operations are repeated until the state “1” is surely reached below the magnetic tube 10 (FIG. 5D). In FIGS. 5A to 5E, the magnetic tube 10 has a length of 6 bits from the reference portion 8 to the lower end (corresponding to 6 magnetic domains and domain walls), so it needs to be repeated 6 times. Finally, all the magnetic tubes 10 can be brought into the state “1” by causing the shift current Is to flow for a time sufficient for the domain wall to reach the upper end of the magnetic tube 10. In this way, the magnetic memory 1 can be initialized.

Such an initialization operation includes, for example, the circuit group shown in FIG. This is realized by connecting to the memory 1. The output of the domain wall motion power supply 20 is bipolar, and a positive current and a negative current can be selected and flowed as necessary. A transistor 35 is provided between the reference unit 18 and the input / output power supply 36. The voltage signal from the input / output controller 32 connected to the gate electrode of the transistor 35 causes the channel of the transistor 35 to become conductive. It is possible to flow current from the input / output power source 36 to the reference unit 18. The output of the input / output power supply 36 is also bipolar. A transistor 37 is also provided between the magnetic tube 10 and the ground line, and a current flows through the magnetic tube 10 unless a voltage signal V _tube from the magnetic tube selection controller 38 is applied to the gate terminal of the transistor 37. There is nothing.

  In such a configuration, the above-described initialization operation is realized, for example, by applying the time-series signals shown in FIGS. 7A to 7D to the magnetic tube 10 and the two transistors 35 and 37. 7A to 7D show timing charts in the case where a positive write current Iw is supplied to each memory cell, that is, information “1” is written to each memory cell.

During the initialization operation, it is necessary to apply a shift or write pulse current to the magnetic tube 10, so that the voltage signal V _tube is always applied to the transistor 37 (FIG. 7C). The write current _{I w} is flowed while the voltage signal _{V IOC} input-output controller 32 is applied (FIG. 7 (b), the FIG. 7 (d)).

(Write operation)
This element can be operated as a memory by combining the initialization operation, the write operation, and the shift operation. This will be described with reference to FIGS. 8A to 8D and FIGS. 9A to 9D. First, the magnetization in the magnetic tube 10 is made uniform using the initialization operation described above (FIG. 8A). At this time, the magnetization in the magnetic tube 10 is aligned in the counterclockwise direction as desired from above the paper surface and is in the state “1”. Here, when a negative write current (−Iw) is passed between the magnetic tube 10 and the reference portion 18, the magnetization of the portion in contact with the reference portion 18 of the magnetic tube 10 is reversed and changes to the state “0” (FIG. 8 (b)). Subsequently, a negative shift current (−Is) is supplied to move the domain wall (domain) to the lower side of the paper by 3 bits (three recording lengths) in the magnetic tube (FIG. 8C). The applied current may be provided with three pulses having a time width for shifting one bit, or may be cut off when the constant current is continuously given and the three-bit shift is completed. Further, a negative write current (-Iw) is again flowed between the magnetic tube 10 and the reference portion 18 to reverse the magnetization of the portion in contact with the reference layer 18 of the magnetic tube 10 (FIG. 8D). With the above operation, the 4-bit information “0110” is stored in the magnetic tube 10.

This operation is represented by timing charts as shown in FIGS. 9A to 9D, for example. Due to the initialization in advance, the write current is not required when writing information "1", only the shift current I _s for the domain wall movement is applied to the magnetic tube 10 (FIG. 9 (a), 9 (B)).

(Read operation)
An example of a method for reading the information stored in the magnetic tube 10 will be described with reference to FIGS. 10 (a) to 10 (e) and FIG. In the magnetic memory 1 of this embodiment, reading of information stored in the magnetic tube 10 is performed by using a tunneling magnetoresistance generated between the reference unit 18 and the magnetic tube 10. Here, it is assumed that the reference unit 18 is magnetized in the direction of the paper surface as in FIGS. 1 (a) and 1 (b). In the state of FIG. 10A, the magnetization of the reference portion 18 and the portion of the magnetic tube 10 in contact with the reference portion 18 is antiparallel, and therefore between the terminal 10 </ b> A of the magnetic tube 10 and the terminal 18 </ b> B of the reference portion 18. The resistance will show a relatively high value. On the other hand, when a shift current Is is passed through the magnetic tube 10 and the domain wall is shifted by one bit above the paper surface, the magnetization of the reference portion 18 and the magnetization direction of the portion in contact with the reference portion 18 of the magnetic tube 10 are parallel. become. For this reason, the tunnel magnetic resistance is reduced, and the resistance between the terminal 10A and the terminal 18B is lower than that in the case where the magnetization arrangement is antiparallel (FIG. 10B). Then, the information stored in the magnetic tube 10 is read by shifting the domain wall position by one bit by the shift current and measuring the resistance between the terminal 10A and the terminal 18B each time (FIG. 10 (c), FIG. 10 (d)). FIG. 11 shows information read in the steps shown in FIGS. 10A to 10D, that is, resistance between the terminal 10A and the terminal 18B. Thus, the information stored in the magnetic tube 10 can be read by shifting the domain wall position by one bit by the shift current and measuring the resistance between the terminal 10A and the terminal 18B each time. The order of information read out by this reading operation is opposite to the order of information stored in the magnetic tube 10. For this reason, the magnetic memory 1 functions as a LIFO (Last-In First-Out) sequential access information recording element.

This read operation is represented by timing charts as shown in FIGS. 12A to 12E, for example. The read current I _R to the magnetic tube 10 via the reference section 18 to read the magnetic information flow from the output power supply 36. The voltage drop V _R at that time is detected by the magnetic information detector 34 converts the magnetic information. At this time, the read current _{I R} must smaller than the write current _{I W} to flow, for example, the read current _{I R} is 1/10 of the write current _{I W.}

(Method of manufacturing magnetic memory)
The magnetic memory 1 of the present embodiment is manufactured by the procedure as shown in FIGS. 13 to 17B, for example. First, as shown in FIG. 17, a wafer substrate 100 made of silicon on which a thermal oxide film (not shown) is formed is prepared. On this wafer substrate 100, a lower wiring 111 made of a Ta underlayer and a Cu layer, a support material layer 112 made of silicon oxide, a reference part magnetic layer 113 made of CoFeB serving as a reference part, and a support made of silicon oxide. A multilayer film 110 in which a material layer 114 and a metal Al layer (mask material layer) 115 serving as a mask for etching are stacked in this order is manufactured using an ultrahigh vacuum sputtering apparatus (FIG. 13). FIG. 13 is a front view of the wafer on which the multilayer film 110 is formed.

A negative resist is applied to the produced multilayer film 110 to form a resist layer (not shown), and then the resist layer is exposed and developed with an ArF immersion exposure apparatus to form a circular hole in the resist layer. To do. Subsequently, the wafer is introduced into a reactive ion etching apparatus (hereinafter also referred to as an RIE apparatus), and a resist layer pattern is transferred to the metal Al layer 115 using a reaction gas mainly composed of BCl ₃ gas. A circular hole is formed on the surface. Thereafter, the wafer is taken out from the RIE apparatus, the resist layer is removed by a wet process, and the wafer is again introduced into the RIE apparatus. Next, a vertical hole is formed in the silicon oxide layer 114 by using the metal Al layer 115 as a mask by using a deep RIE process using CHF ₃ gas. This process is stopped once when the reference magnetic layer 113 is reached. Next, the reaction gas is switched again to a gas mainly composed of BCl ₃ , and a vertical hole is also formed in the reference part magnetic layer 113. When the vertical hole penetrates the reference magnetic layer 113, the reaction gas is switched to a gas mainly composed of CHF ₃ and the vertical hole 116 is formed in the silicon oxide layer 112 until the lower wiring 111 is reached again by the vertical RIE process. (FIGS. 14A and 14B). 14A and 14B are a front view and a top view of the wafer.

  Next, the wafer is introduced into an atomic layer deposition apparatus (hereinafter also referred to as an ALD apparatus), and a uniform Mg layer is formed on the entire wafer surface including the vertical holes 116. After the Mg layer is deposited, the wafer is introduced into an ultra-high vacuum apparatus without being exposed to the atmosphere, and oxygen plasma is irradiated onto the wafer surface to form an Mg oxide film 117 on the entire wafer surface including the vertical holes 116. Further, the wafer is again introduced into the ALD apparatus without being exposed to the atmosphere, and uniform CoFeB 118 is formed on the entire surface of the wafer including the vertical holes 116. The wafer taken out from the ALD apparatus removes the extra CoFeB layer and Mg oxide layer formed on the wafer by the chemical mechanical polishing process (CMP) and the metal Al layer 115 as a mask (FIG. 15A, FIG. 15). b)). FIGS. 15A and 15B are a front view and a top view of the wafer after the metal Al layer 115 is removed, respectively.

  The resist is applied again to form a resist layer (not shown) and introduced into an ArF immersion exposure apparatus. Here, a pattern in which the shape of the magnetic tube and the reference portion are superimposed is exposed and developed. Subsequently, the wafer is introduced into an Ar ion milling apparatus, milling is performed using the resist layer as a mask, milling is performed until the upper surface of the lower wiring 112 is exposed, and then the wafer is taken out from the ion milling apparatus (FIG. 16A ), 16 (b)). FIGS. 16A and 16B are a front view and a top view of the wafer.

  The wafer was introduced into the oxidizer with the resist layer attached, and the arc portion of the reference portion magnetic layer 113 was all oxidized as shown in FIGS. 17A and 17B, and the oxidized layer 119 and The oxidation process is performed on the wafer until it is. As a result, the magnetic memory 1 of the first embodiment is formed. FIG. 17A and FIG. 17B are a front view and a top view of the wafer.

In addition, by using a material with a significantly different coefficient of thermal expansion as the material 118 constituting the magnetic tube and the material used for the support material layers 112 and 114, the stress change to the magnetic tube at the production temperature and room temperature when the magnetic tube is formed can be measured. By utilizing this, anisotropy in the major axis direction (direction in which the magnetic tube extends) can be imparted to the magnetic tube via the magnetostrictive effect, thereby stabilizing the operation. For example, when a magnetic tube having an inner diameter of 50 nm and a thickness of 5 nm is formed of a ferromagnetic material having a magnetization size of 800 emu / cc, the z-axis direction becomes the hard axis of magnetization, and the energy difference is about 5 × 10 ⁶ emu / cc. It is good to make it above.

  Thus, the magnetic memory of the first embodiment can be manufactured by a simple manufacturing method compared to the conventional domain wall memory, and the manufacturing cost can be reduced.

  In the first embodiment, as shown in FIGS. 1A and 1B, the magnetic tube 10 has an annular cross section (a cross section parallel to the xy plane shown in FIG. 1A). In addition, the size (diameter) of the outer shape and inner diameter was constant. That is, the outer shape and the inner diameter were each a constant cylindrical shape. The shape of the magnetic tube 10 is not limited to the shape shown in FIGS. 1 (a) and 1 (b). For example, the periodic shapes shown in FIGS. 18A to 18C may be taken. FIG. 18A shows a longitudinal sectional view of the magnetic tube 10 of the first example (a section parallel to the yz plane shown in FIG. 1A). In the magnetic tube 10 of the first example, the cross section of the magnetic tube 10 (the cross section parallel to the xy plane shown in FIG. 1A) is an annular shape and in the cross section as in the first embodiment. Although the wall thickness is also constant, the shape of the outer diameter and the inner diameter changes periodically along the direction in which the magnetic tube 10 extends (the z-axis direction shown in FIG. 1A) ( FIG. 18 (a)). FIG. 18B shows a longitudinal sectional view of the magnetic tube 10 of the second example. The magnetic tube 10 of the second example has an annular shape as in the first embodiment, but the outer diameter is constant and the inner diameter is along the direction in which the magnetic tube 10 extends. The shape changes periodically (FIG. 18B). FIG. 18C shows a longitudinal sectional view of the magnetic tube 10 of the third example. The magnetic tube 10 of this third example has an annular shape in cross section as in the first embodiment, but the size of the inner diameter is constant and the size of the outer diameter is along the direction in which the magnetic tube 10 extends. The shape changes periodically (FIG. 18C). In the magnetic tube shown in FIGS. 18A to 18C, the period of the shape corresponds to the length (recording length) that can be accommodated by 1 bit. In the magnetic tube 10 shown in FIGS. 18 (a) and 18 (c), a domain wall is easily formed at a location where the outer diameter is narrow, and in the magnetic tube 10 shown in FIG. 18 (b), the inner diameter is maximum. It is easy to form a domain wall at this point. For this reason, by forming the magnetic tube 1 as shown in FIGS. 18A to 18C, the length of the recording length can be set with high accuracy.

  As described above, according to the first embodiment, it is possible to provide a magnetic memory capable of reducing the manufacturing cost.

(Second Embodiment)
A magnetic memory according to the second embodiment will be described with reference to FIGS. 19 (a) to 20 (b). The magnetic memory according to the second embodiment has a configuration in which a plurality of reference portions 18 are provided in one magnetic tube 10 shown in the first embodiment. As in the magnetic memory of the second embodiment, by providing a plurality of reference portions on one magnetic tube, the magnetic tube can be effectively used in terms of recording capacity.

  FIGS. 19A and 19B show the magnetic memory 1 according to the first embodiment provided with one reference unit 8. Here, the magnetic memory 1 having a length that allows the magnetic tube 10 to form a magnetic domain for 37 bits is taken as an example. If the portion of the magnetic tube 10 adjacent to the reference portion 18 is used only for writing and reading, the magnetic tube 10 can store 36-bit information. As already described, the magnetic memory 1 involves a shift operation for reading. Therefore, a portion serving as a buffer for saving the shifted bit is required for the magnetic tube 10. The length of the buffer is required to accommodate the information to be read. Therefore, when one reference portion 18 is provided, it is optimal to place the reference portion 18 at the midpoint of the magnetic tube 10 as shown in FIG. However, even in the optimum case, the utilization rate of the magnetic tube 10 as a recording medium is at most about 50%.

  On the other hand, the magnetic memory 1 of the second embodiment has a large recording capacity when a plurality of reference portions 18a, 18b, and 18c are provided in one magnetic tube 10, as shown in FIGS. Become. An intermediate layer is provided between each of the reference portions 18a, 18b, and 18c and the magnetic tube 10 as in the case of the first embodiment. As shown in FIGS. 20A and 20B, three reference portions 18a, 18b, and 18c are arranged at equal intervals. The length of the magnetic tube 10 that can be recorded is 36 bits as in FIGS. 19 (a) and 19 (b), and is divided into four equal parts by 9 bits by each reference unit 18. In this case, it is only necessary to perform a maximum 9-bit shift for the write and read operations. Therefore, 27 bits can be stored in three sections from the top of the magnetic tube 10 shown in FIGS. 20A and 20B, and the last section below the reference unit 18c can be used as a buffer. . As a result, even when the same magnetic tube 10 shown in FIGS. 19 (a) and 19 (b) is used, the utilization rate can be increased to 75% by providing the three reference portions 18a, 18b, and 18c. When the number is increased while the distances between the reference portions 18a, 18b, and 18c are made uniform, the utilization rate approaches 100%.

  As described above, the magnetic memory of the second embodiment has the same structure as that of the magnetic memory of the first embodiment except that there are a plurality of reference portions, and thus the manufacturing cost can be reduced.

(Third embodiment)
A magnetic memory according to the third embodiment will be described with reference to FIGS. A top view of the magnetic memory of the third embodiment is shown in FIG. The magnetic memory 1 according to the third embodiment includes a plurality of magnetic tubes 10 ₁ to 10 ₄ arranged in a line in a direction orthogonal to the extending direction, a plurality of intermediate layers 16A _{1 to} 16A _8, and a plurality of writings. and a use reference portion _18A 1 _{~18A 5.} Intermediate layers 16A _2i-1 and 16A _2i are provided on both sides of each magnetic tube 10 _i (i = 1 to 4). The magnetic tube 10 ₁ relative to the intermediate layer A16 ₁ reference portion 18A ₁ is provided on the opposite side. Also, the reference unit 18A ₂ provided between the intermediate layer 16A ₂ and the intermediate layer 16A _3, the reference unit 18A ₂ is shared between the magnetic tubes ₁₀ 1, 10 _2. See section A18 ₃ is provided between the intermediate layer 16A ₄ and the intermediate layer 16A _5, the reference unit 18A ₃ are shared between the magnetic tubes ₁₀ 2, 10 _3. A reference portion 18A ₄ is provided between the intermediate layer 16A ₆ and the intermediate layer 16A _7, and the reference portion 18A ₄ is shared between the magnetic tubes 10 ₃ and 10 ₄ . Further, the reference portions 18A ₅ on the opposite side is provided with the magnetic tube 10 ₄ with respect to the intermediate layer 16A _8. That is, a reference portion is provided on both sides of each magnetic tube in the direction in which the plurality of magnetic tubes are arranged via an intermediate layer, and the reference portion provided between adjacent magnetic tubes is connected to the adjacent magnetic tubes. It becomes the composition to share.

In the magnetic memory according to the third embodiment having such a configuration, information can be written to the plurality of magnetic tubes 10 ₁ to 10 ₄ at a time. The material of the intermediate layer provided between the reference portion and the magnetic tube may be either a tunnel insulating film material or a nonmagnetic metal material, as described in the first embodiment. However, it is preferable to use a non-magnetic metal material in order to prevent the resistance from becoming too high when a large number of magnetic tubes are connected as in the third embodiment. However, in this case, in order to prevent parasitic conduction by the intermediate layer, the intermediate layers 16A _2I-1 and 16A _2i provided on both sides of each magnetic tube 10 _i (i = 1 to 4) are not provided as shown in FIG. It is desirable that they are continuously separated from each other.

A front view of the magnetic memory of the third embodiment is shown in FIG. 22, and a bottom view is shown in FIG. In the third embodiment, since the writing reference portions 18A _{1 to} 18A ₅ connect the magnetic tubes 10 ₁ to 10 ₄ in series, the magnetization state of each magnetic tube is converted into an electric signal using the magnetoresistance effect. Not suitable for conversion purposes. For this reason, the magnetic memory 1 according to the third embodiment includes a read reference unit 18B _i for each magnetic tube 10 _i (i = 1 to 4).

The magnetic memory of the third embodiment, write information to the magnetic tube 10 ₁ to 10 ₄ by applying a current between the right end of the reference portion 18A ₁ and the left end of the reference portion 18A ₅ for writing for writing. Figure as indicated at 24, all of the write reference portion _18A 1 _~18A magnetizing a reference for writing a write current in a state in which upward from the right end of the reference portion 18A ₁ for writing the left edge of the 24 portions of ₅ 18A ₅ Current is passed through. Then, as shown in FIG. 25, the magnetization of the portion (shaded portion) of the magnetic tube 10 _{i in} the vicinity of each reference portion 18A _i (i = 1 to 5) is magnetized counterclockwise, and all the magnetic tubes 10 ₁ to 10 ₁ 10 ₄ information "1" is written. At this time, the spin torque that prompts the magnetization of the right portion of each magnetic tube 10 _i (i = 1 to 4) to be anti-parallel to the reference portion 18A _i is parallel to the magnetization of the left portion. The spin torque that urges you to work. Therefore, it is possible to efficiently reverse the magnetization with a lower current value as compared with the case where the reference portion is provided only on one side of the magnetic tube and the current flows.

Further, in the third embodiment, the magnetic tubes 10 ₁ to 10 ₄ are connected in series by the reference portions 18A _{1 to} 18A _5, so that 1/1 compared to writing information one by one in each magnetic tube. Information “1” can be recorded with a current amount of four. Further, each of the reference portions 18A _{2 to} 18A ₄ provided between the adjacent magnetic tubes may be separated into two by the nonmagnetic metal layer 17, as shown in FIG. In this case, the action of the spin torque generated in the reference portion during the writing operation on the adjacent magnetic tube can be reduced.

On the other hand, in the third embodiment, since the same information is written to all the magnetic tubes at once, a device is required for the shift operation in order to complete the write operation. An example of the write operation of the magnetic memory 1 according to the third embodiment will be described with reference to FIGS. 26 to 129. First, as shown in FIGS. 24 and 25, information “1” is written in all the magnetic tubes 10 ₁ to 10 ₄ .

Then, shifting by one bit the domain wall by passing the magnetic tube 10 ₂ to 10 ₄ to write the negative shift current (-Is) to leave the magnetic tube to be written the information "1". As a result, information “1” is written in the magnetic tubes 10 ₂ to 10 ₄ . In this case it does not flow shift current to the magnetic tube 10 ₁ with no need to write the original information "1".

Subsequently, it flowed negative write current (-Iw) between the left end of the reference portion 18A ₁ and the right end of the reference portion 18A ₅ for writing for writing, write data "0", the shift only the magnetic tube to be saved current (Fig. 27). In the case shown in FIG. 27, a shift current is passed through the magnetic tubes 10 ₁ to 10 ₃ . As a result, the information recorded in the magnetic tubes 10 ₁ , 10 ₂ , 10 ₃ , and 10 ₄ at this time becomes “0”, “10”, “10”, and “1”, respectively.

Next, FIG. 28 shows a situation obtained as a result of flowing the write current Iw again and further passing the shift current to the magnetic tubes 10 ₁ , 10 ₃ , 10 ₄ . By this operation, information of “01”, “10”, “101”, “11” is stored in the magnetic tubes 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ , respectively.

Furthermore, as shown in FIG. 29, when the write current −Iw is applied and the bits of the magnetic tubes 10 ₁ , 10 ₂ , and 10 ₄ are shifted by the shift current, the magnetic tubes 10 ₁ , 10 ₂ , 10 ₃ , and 10 ₄ are changed. Respectively, information of 3 bits of “010”, “100”, “101”, and “110” is input. As described above, when the plurality of magnetic tubes 10 ₁ to 10 ₄ are connected in series by the write reference units 18A _{1 to} 18A ₅ to enable the collective write operation, not only the write current can be effectively used but also the write operation. It is also possible to prevent an erroneous shift operation due to.

The collective writing operation to the plurality of magnetic tubes in the magnetic memory of the third embodiment is performed by, for example, the circuit group shown in FIG. 30, that is, the domain wall motion power supply 30, the input controller 32A, the output controller 32B, and the magnetic information detector 34. This can be implemented by connecting the input power source 36A, the output power source 36B, and the magnetic tube selection controller 38 to the magnetic memory 1. The domain wall motion power source 30 and the input power source 36A are bipolar outputs, and a positive direction current and a negative direction current can be selected and passed as required. In Figure 30, the input power supply 36A to the reference unit 18A ₅ for the right end of the writing of the magnetic memory 1 is connected, it is connected to the ground line to the left end of the reference portion 18A ₁ for writing via the transistor 35A. The channel of the transistor 35A is turned on by the voltage signal V _IC from the input controller 32A connected to the gate terminal of the transistor 35A, and current can be supplied from the input power supply 36A to the reference unit 18A5.

The read reference units 18B _{1 to} 18B ₄ are each connected to the magnetic information detector 34 and also connected to the output power supply 36B via the transistor 35B. The voltage signal V _OC from the output controller 32B connected to the gate terminal of the transistor 35B, the transistor 35B is turned on, by flowing the read current I _R is, magnetic information V _R is detected by the magnetic information detector 34 Read out.

A transistor 37 _i is also provided between each magnetic tube 10 _i (i = 1 to 4) and the ground line. As long as the voltage signal V _tubei from the magnetic tube selection controller 38 is not applied to the gate terminal of each transistor 37 _i (i = 1 to 4), no current flows through the magnetic tube 10 _i .

In such a configuration, once the write operation described above, by providing in FIG. 31 (a) to 31 magnetic tube ₁₀ a time-series signal shown in (i) 1 ~10 ₄ and transistor _35A, 37 1 to 37 ₄ for example Realized. The write current _Iw is supplied while the voltage signal V _IC of the input controller 32A is being applied.

Magnetic tube should read magnetic information, for example, a magnetic tube 10 ₁ is selected by the magnetic tube selection controller 38. This selection is performed by applying a voltage signal Vtube1 from magnetic tube selection controller 38 to the transistor 37 _1. Thereafter, by applying a voltage signal _{V OC} from the output controller 32B to the gate terminal of the transistor 35B, flow the read current _{I R} to the magnetic tube 10 ₁ through the reference part 18B ₁ from the output power supply 36B. The voltage drop V _R at that time is detected by the magnetic information detector 34 converts the magnetic information. At this time, the read current _{I R} must smaller than the write current _{I W} to flow, for example, the read current _{I R} is 1/10 of the write current _{I W.}

  As described above, the magnetic memory of the third embodiment has the same structure as that of the magnetic memory of the first embodiment except that there are a plurality of magnetic tubes and reference parts, so that the manufacturing cost is reduced. Can do.

(Fourth embodiment)
The direction of magnetization of the magnetic tube and the reference portion may be the z-axis direction. In this case, initialization can be performed by applying external magnetization in the z-axis direction, and other operations can be performed in the same procedure as described in the above embodiment.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

1 magnetic memory 10 the magnetic tube 10 ₁ to 10 ₄ magnetic tube 16 intermediate layer 16A ₁ ~16A ₈ intermediate layer 18 reference portion 18A ₁ ~18A ₅ reference section for writing 18B ₁ ～18B ₄ read reference unit

Claims (15)

A magnetic structure extending in a first direction and having a circular cross section in a plane perpendicular to the first direction;
A nonmagnetic layer provided on an outer surface along the first direction of the magnetic structure;
A reference portion including a magnetic body provided on a part of the surface of the nonmagnetic layer opposite to the magnetic body structure;
A first circuit capable of flowing a first current bidirectionally along the first direction in the magnetic structure;
A second circuit capable of causing a second current to flow bidirectionally through the nonmagnetic layer between the magnetic structure and the reference portion;
A third circuit for passing a third current smaller than an absolute value of the second current through the nonmagnetic layer between the magnetic structure and the reference portion;
A fourth circuit for detecting a voltage generated between the magnetic body structure and the reference portion via the nonmagnetic layer when the third current is passed;
With magnetic memory. By passing the second current, after storing information in a region of the magnetic structure that is in contact with the reference portion via the nonmagnetic layer, the write operation is performed by passing the first current. The magnetic memory according to claim 1 . Based on the voltage detected by the fourth circuit by flowing the third current, the information stored in the region of the magnetic material structure in contact with the reference portion through the nonmagnetic layer is read. the magnetic memory according to claim 1, wherein intends row Te. Regarding the region where the reference portion is in contact with the outer surface of the magnetic structure via the nonmagnetic layer, the angle of view as viewed from the center of the cross section of the magnetic structure in a plane orthogonal to the first direction is less than 180 degrees the magnetic memory according to any one of der Ru claims 1 to 3. Wherein the reference portion is a magnetic memory according to any one of claims 1 to 4 in the first direction of the magnetic structure that provided a plurality. The thickness in the first direction, the magnetic memory according to any one of claims 1 to 5 Ru der than 50nm or less 10nm of the magnetic of the reference portion. Said magnetic structure, said a wall thickness in the cross-section is constant, the size of the outer diameter and inner diameter is in the first direction, any one of claims 1 to 6 that have a periodically changing shape The magnetic memory described in 1. The magnetic structure, the magnetic memory according to any one of claims 1 to 6 size outer diameter that has a shape in which the size of the constant and the inner diameter varies periodically along the first direction. The magnetic structure, the magnetic memory according to any one size and OD of inner diameter at constant of claims 1 to 6 that have a shape that periodically changes along the first direction. A plurality of magnetic body structures each extending in a first direction and having a circular cross section in a plane orthogonal to the first direction, and arranged in a row in a second direction orthogonal to the first direction Magnetic structure of
Corresponding to each of the plurality of magnetic body structures, there are a plurality of first reference portions provided on both sides in the second direction of each magnetic body structure, and each of the first reference portions includes a plurality of magnetic bodies. A first reference part;
A plurality of first nonmagnetic layers provided between each of the plurality of magnetic body structures and a corresponding first reference portion;
A plurality of second nonmagnetic layers provided on an outer surface along the first direction of each magnetic structure corresponding to each of the plurality of magnetic structures;
A plurality of second reference portions provided corresponding to each of the plurality of magnetic body structures, each having a magnetic body, wherein each of the second reference portions is opposite to the corresponding magnetic body structure. A plurality of second reference portions provided on a part of the surface of the non-magnetic layer;
With
Wherein the plurality of magnetic structures, said plurality of first reference portion and a plurality of first magnetic memory that is electrically connected via a non-magnetic layer. Adjacent each provided corresponding to the magnetic structure, the adjacent magnetic memories opposing two first reference section which is disposed on a side of the integral der Ru claim 10, wherein the magnetic structure. It provided corresponding to adjacent magnetic structure, of the first reference portion opposed two disposed on the side of the adjacent magnetic structure according to claim 10, wherein it is connected via a non-magnetic metal layer Magnetic memory. A first circuit capable of selecting each of the plurality of magnetic body structures and allowing a first current to flow bidirectionally along the first direction through the selected magnetic body structures;
A second circuit capable of causing a second current to flow in both directions through the plurality of magnetic structures electrically connected via the plurality of first reference portions and the plurality of first nonmagnetic layers;
A third circuit that selects one of the plurality of magnetic structures and causes a third current smaller than the absolute value of the second current to flow through the selected magnetic structure;
A fourth circuit for detecting a voltage generated via the second nonmagnetic layer between the selected magnetic body structure and the second reference portion when the third current is passed;
The magnetic memory according to any one of claims 10 to 12 that further comprise a. By passing the second current, information is stored in a region of the plurality of magnetic structures that are in contact with the second reference portion via the second nonmagnetic layer, and then the selected magnetic structure is formed. wherein by supplying a first current, a magnetic memory according to claim 13, wherein intends row write operation. Reading the information stored in the region in contact with the second reference portion via the second nonmagnetic layer of the selected magnetic structure, by passing the third current, the fourth circuit the magnetic memory according to claim 13, wherein intends rows based on the voltage detected by.

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